Ever since the end of the war, based on the realization that Japan is a country lacking resources such as metallic minerals, Japan has developed its economy by importing necessary minerals and the like. However, for the past several years, events that pose an obstacle to economic development such as the output limitation imposed by mineral-producing countries and a steep rise of prices have occurred. Against such a background, ocean floor resources in the seas close to Japan having the sixth largest exclusive economic zone (EEZ) in the world and 50 or more hydrothermal activity areas that serve as mineral sources are attracting even more attention.
There has been a basic scientific achievement saying that ocean floor resources including ocean floor hydrothermal minerals are rich with rare metal elements or rare earth elements. Based on the above-described achievement, a national strategy to estimate the reservoir of domestic ocean floor resources is becoming more important. However, in actuality, there are extremely huge problems with the technological development, profitability, and environmental impact assessment in steps for developing an ocean floor hydrothermal activity area from which ocean floor hydrothermal minerals are produced as a mineral deposit, mining resources, and putting the resources into practical use. As a result, there are only a few venture companies that are actually making any effort to recover resources from the ocean floor.
For the recovery of resources from the ocean floor, a series of operation steps such as the disposition of a special heavy machine on the ocean floor, the mining operation using the above-described heavy machine, and the transportation of rocks and/or sediment containing minerals to above the sea are assumed (refer to Non-Patent Literature 1). Studies are also underway regarding a method for extracting ocean floor minerals by sending hot water ejecting from the ocean floor to a mother ship on the sea using a pipe (refer to Patent Literature 1 and 2).